There are three culprits to the burnt coffee taste so highly prized among gas station cafes:
- Coffee that's over roasted, or where the roast profile heats up too quickly. While some of us love a great dark roast, too much of a good thing can end up tasting bitter and/or burned in the cup.
- Coffee that's stale (i.e. spoiled, or over a week or so past roasting for dark coffees) will also taste bitter and/or burned in the cup.
- Once brewed, the heat plates on most drip brewers are a flavor killer. The idea is to keep coffee warm, but prolonged exposure will literally cook the coffee, producing the ultimate in burned coffee taste.
Avoiding burnt coffee is pretty simple: look for small batch roasting that isn't ultra dark; use fresh beans; and don't leave the pot on the heater all morning!